The present invention relates to a device and a method for magnetron cathode sputtering for producing coatings on a substrate by means of a sputtering cathode, which can be arranged in a vacuum chamber and preferably comprises, with respect to the center axis of the sputtering cathode, pole shoes, a target and at least one concentrically or annularly arranged magnet.
A device for cathode sputtering for the static coating of disk-shaped substrates by means of a plasma in a vacuum chamber with at least one opening, which can be closed from the outside by placing a sputtering cathode on it, is already known (DE 43 15 023 A1). An elastic vacuum seal ring and an annular anode are provided between the cathode and the chamber wall, which radially enclose the openings from the outside, wherein the anode has a flat contact surface on its surface facing the cathode. The known sputtering cathode consists of a disk-shaped ferromagnetic yoke and a cooling plate. A disk-shaped insulator is inserted between these two. The target to be sputtered is arranged in front of the cooling plate, while an annularly arranged magnet is inserted in a groove on the back of the cooling plate. A counter-magnetic field is generated by the annularly arranged magnet, which affects the path of the magnetic field lines. By means of this, the path of the magnetic field lines is given an approximately parallel or lens-shaped or convex form.
U.S. Pat. No. 5,262,030 discloses a magnetron sputtering cathode with a variable magnetic field during coating. The magnetic field determines that area of the target from which the material is ejected. For this purpose, an arrangement is provided which comprises several magnets which are arranged behind the sputtering cathode and can selectively be switched on and off for generating or not a magnetic field being parallel to the surface of the target. Overlapping causes the magnetic field to move radially outwardly or over specific areas of the target. Since predetermined magnetic fields are switched on or off, the magnetic field in the area of the target surface is varied discontinuously.
U.S. Pat. No. 3,956,093 relates to a method and a device for magnetron cathode sputtering comprising a sputtering cathode arranged in a vacuum chamber, pole shoes, a target and a magnetic field in the area of the target surface generated in that a variable magnetic field superimposes a static magnetic field. The variable magnetic field is generated by coils arranged in one plane with the target.
U.S. Pat. No. 5,182,001 discloses a method for coating substrates by magnetron cathode sputtering. The method provides a variable magnetic field in the area of the target surface generated by a coil in that a variable magnetic field overlaps a static magnetic field. The permanent magnets generating the static magnetic field have poles provided on the one hand outside the outer edge of the target and, on the other hand, inside the inner edge of the target. In the outer area of the permanent magnet at the outer edge of the target a magnetic coil for generating the variable magnetic field is provided, said magnetic coil extending vertically over the target surface.
It is an object of the present invention to provide an improved cathode sputtering device and an improved cathode sputtering method, wherein the target yield is improved and, at the same time, a very constant coating thickness is achieved.
This object is achieved by the features of the claims.
In order to be adapted to the shape of the substrate, the cathode, the target, the yoke and the magnet arrangement can take, for example, an annular, rectangular, elliptical or any other shape if the substrate has, for example, a circular, rectangular, elliptical or any other shape.
Preferably, at least one further means generating a continuously variable magnetic field is provided in the area of the target next to the magnets arranged in accordance with the shape of the substrate. Due to the advantageous arrangement of the magnet next to the means generating a variable magnetic field, a constant coating thickness is achieved even if the substrates have different sizes, wherein the coating thickness can deviate between xc2x12% to 3%. The sputtering groove is formed in accordance with the preset magnetic field. With this magnet arrangement in connection with the means generating a variable magnetic field, the main magnetic field is generated such that throughout the entire process the erosion groove can be influenced purposefully.
Due to the advantageous arrangement of the, for example, annularly arranged magnet, in connection with the means generating a variable magnetic field or with at least one coil, the magnetic field is continuously varied, in particular in the area of the target surface. In this connection, the magnetic flux lines extend from the center to outside or from outside to inside and take a lens-shaped course, so that an erosion groove being as large as possible is obtained. If a concave erosion groove is obtained after a considerably long process, it is advantageous that the magnetic field lines take a course being approximately parallel with respect to the surface of the target. A shielding plate prevents the magnetic field lines from entering the yoke. Advantageously, these coils can also be controlled in accordance with time so that it is possible to vary, on the one hand, the service life of the target and, on the other hand, the magnetic field during a cycle time. For example, a control curve (f(I)=I(t)) can be determined empirically, which control curve guarantees that, on the one hand, the substrate is coated very constantly and, on the other hand, the target is exploited optimally. The empirically determined control curve, for example for a gold target, can then repeatedly be used for the coating process. The control operation for the coating process can also be controlled by a program.
By means of the coils used in the present invention, a variable magnetic field may be generated very economically.
It is essential for the present invention that due to the use of magnetic coils, the magnetic field in the target space is controlled and varied purposefully so that the plasma can be displaced radially from inside to outside. The erosion groove can therefore be displaced radially over the target or can be changed; it is thus possible to produce, on the one hand, a very wide erosion groove by continuously varying the magnetic field or, on the other hand, two erosion grooves next to each other by stepwise switching the magnetic field back and forth.
Moreover, it is advantageous that at least a first coil or, for example, an annularly arranged coil is provided between the target or between the back surface of the target and the yoke plate.
In a further embodiment of the device according to the invention it is furthermore possible that at least one annularly arranged magnet is provided in the area of the yoke plate or in the area of the outer circumference of the yoke plate.
In a further embodiment of the invention it is advantageous that the first magnetic coil is provided in the area of the outer circumference of the target and the second magnetic coil is provided in the area of the cooling head.
According to a preferred embodiment of the solution according to the invention, the two magnetic coils are eventually provided slightly above the upper limit or the back surface of the target.
It is of particular importance for the present invention that the two magnetic coils are arranged in the same transverse plane.
In connection with the embodiment and arrangement of the invention it is advantageous that the two magnetic coils are arranged in the same transverse plane between a first or a second yoke plate and the back surface of the target.
Moreover, it is advantageous that the, for example annularly arranged magnet provided in the area of the outer circumference of the first and/or second yoke or yoke plate is provided between the lower or first yoke plate and the upper or second yoke plate.
In addition, it is advantageous that the two magnetic coils and the annularly arranged magnet are arranged concentrically with respect to the center axis of the sputtering cathode.
To this end it is advantageous that the annularly arranged magnet has an outer diameter which is approximately as large as, smaller or larger than the outer diameter of the first coil.
Moreover, it is advantageous that in an insulator provided between a target or at least one yoke plate and/or in the target ring chambers for receiving the coil or annularly arranged coils are provided.
In a further embodiment of the device according to the invention it is also possible that the two coils or annularly arranged coils have different diameters.
According to a further embodiment of the invention it is advantageous that the second annularly arranged coil has a smaller outer diameter than the first coil.
The arrangement according to the invention guarantees that the annularly arranged magnet has an N/S polarity directed towards the substrate.
In a further embodiment of the invention it is advantageous that a shielding means is provided between the two coils.
According to a further embodiment of the drive means of the present invention it is also possible that the shielding means is provided between one of the yoke plates and the target.
Moreover, it is advantageous that the shielding means is provided between one of the yoke plates and/or an insulator and the target.
An essential, advantageous embodiment is achieved in that the two yoke plates are spaced from each other with respect to the center axis.
Moreover, it is advantageous that the distance between the two yoke plates corresponds approximately to the height of the annularly arranged magnet.
Furthermore, it is advantageous that the two yoke plates have different outer diameters or that they are arranged In the form of a step.
According to a further development of the device according to the invention it is furthermore possible that the yoke plate having a smaller outer diameter is connected with the cooling finger and the yoke plate having a larger outer diameter is connected indirectly or directly with the pole shoe.
Preferably, sensors are provided for determining the coating thickness on the substrate, the shape of the target surface and/or the shape of the magnetic field.
To this end it is advantageous that the current fed to the coils can be varied depending on the time and/or the sensor signals.
Moreover, it is advantageous that the current fed to the coils or the current supply to the coils can be controlled via a control curve or a preset program and that for this purpose current conductors are in an operating connection with a computer via a current divider.
Advantageously, the sputtering energy can be set on the target depending on place and time so that a very constant coating and target exploitation can be achieved. Moreover, the coating process can be monitored and controlled during the process.